P8 Space Physics

Question 1

How does a main sequence star form?

Answer 1

1. Stars initially form from a cloud of dust and gas called a nebula
2. The force of gravity pulls the dust and gas together to form a protostar. The temperature rises as the star gets denser and more particles collide with each other. When hot enough, nuclear fusion occurs with hydrogen nuclei forming helium nuclei.
3. The star is now in a long stable period where the outward pressure caused by nuclear fusion balances the force of gravity pulling everything inwards

Question 2

What happens to a small star when hydrogen runs out?

Answer 2

1. It swells into a red giant because the surface cools. Heavier elements are created in the core
2. The star then becomes unstable and ejects it s outer layer of dust and gas, leaving behind a hot, dense sold core - a white dwarf
3. As as white dwarf cools, it emits less and less energy until it becomes a black dwarf

Question 3

What happens to a large star when hydrogen runs out?

Answer 3

1. The stars glow brightly and expand and contract several times. Eventually, they explode in a supernova, ejecting heavy elements which forms new planets and stars
2. The exploding supernova throws the outer layers of dust and gas into space, leaving a very dense core called a neutron star. If a star is massive enough, it will become a black hole

Question 4

What is the big bang theory?

Answer 4

The theory that all matter in the universe occupied a very small space which was very dense and very hot. It then exploded and space started expanding

Question 5

What is red-shift?

Answer 5

Light from distant galaxies are shifted towards the red end of the spectrum, suggesting the source of light is moving away from us. The greater the red-shift, the faster the galaxies are moving away